1. Field of the invention
This invention relates to alicyclic compounds useful in topical contraception. They appear to have a predominantly spermicidal action, but to some extent also have a mucospissic (mucus-thickening) effect which inhibits the movement of sperm in the cervical canal. The mucus-thickening effect enables the compounds to be used for various therapeutic purposes.
2. Description of prior art
Mucus is secreted in many different parts of the human body. For example, the stomach has a thick lining of mucus which protects the epithelial cells from attack. Damage to the mucus lining is believed to play a part in gastric ulceration. It is also secreted in the cervix where it has an important role in conception. In the middle of the menstrual cycle the mucus has low visco-elasticity, favouring penetration of sperm at a time which is essential for conception, but at other times in the cycle it thickens and thereby acts to some extent as a natural contraceptive by impeding the passage of sperm to the womb. It would be desirable to thicken gastric mucus to counteract ulcers and also cervical mucus for the purposes of contraception. The latter objective has taken on greater importance in view of the increasing use of the protective sheaths brought about by the fear of acquired immune deficiency syndrome (AIDS). The use of an agent for thickening cervical mucus would provide an additional barrier to sperm, either instead of or in addition to a spermicidal agent.
Relatively little research has been devoted to additives for thickening mucus. C. Marriott and I.W. Kellaway. Biorheology 12, 391-395 (1975) reported that tetracycline and three derivatives thereof increased the thickness of bronchial mucus. S.S. Davis and L.C. Deverell, Mod. Probl. Pediat. 19, 207-217 (1977), showed that sodium tetraborate. Congo red and tetracycline are mucospissic agents. V.P. Kamboj et al., Indian J. Exp. Biol. 17, 1379-1380 (1977) showed that various plant extracts reduced the migration of sperm through cervical mucus. M. Saga et al., St. Marianna Med. J. 7, 146-150 (1979) have showed that calcium ions, spermine, polylysine and lysozyme all thicken human cervical mucus. These authors claim that these highly basic, cationic additives interact with acidic, negatively charged mucin molecules. According to L. Batallan et al.. Contraception-fertilite-sexualite 8, 735-739 (1980), the modern era of vaginal chemical contraception began with surfactants, with the introduction of a spermicide containing dimethyl alkyl benzyl ammonium chloride. Experiments by Batallon et al. on this spermicide indicated that this compound might act to modify the structure of the cervical mucus. U.S. Pat. No. 4,590.070 (Chantler et al. assigned to ICI) claims a contraceptive method depending on the application to the vagina of a linear polymer of formula --X.NH.C(.dbd.NH) NH.C(.dbd.NH). NH.Y. NH.C(.dbd.NH). NH.C(.dbd.NH)NH-- wherein X and Y are bridging groups in which together the total number of carbon atoms directly interposed between adjacent nitrogen atoms is greater than 9 and less than 17, or an acid addition salt thereof.
It has been a problem to provide an alternative contraceptive agent.
Further prior art is discussed after the "Summary of the invention", without which its context would not be clear.